How to Use Arrays.sort in Java: Simple Guide

Use Arrays.sort(array) to sort an array in Java in ascending order. It works for arrays of primitives and objects that implement Comparable. For custom sorting, use Arrays.sort(array, Comparator).

Syntax

The basic syntax to sort an array is:

• Arrays.sort(array): Sorts the array in ascending order.
• Arrays.sort(array, fromIndex, toIndex): Sorts a range within the array.
• Arrays.sort(array, Comparator): Sorts objects using a custom rule.

java

import java.util.Arrays;

// Sort entire array
Arrays.sort(array);

// Sort part of array
Arrays.sort(array, fromIndex, toIndex);

// Sort with custom comparator
Arrays.sort(array, (a, b) -> a.compareTo(b));

Example

This example shows how to sort an integer array and a string array using Arrays.sort. The integer array is sorted in ascending order, and the string array is sorted alphabetically.

java

import java.util.Arrays;

public class SortExample {
    public static void main(String[] args) {
        int[] numbers = {5, 3, 8, 1, 2};
        String[] fruits = {"banana", "apple", "orange"};

        Arrays.sort(numbers);
        Arrays.sort(fruits);

        System.out.println("Sorted numbers: " + Arrays.toString(numbers));
        System.out.println("Sorted fruits: " + Arrays.toString(fruits));
    }
}

Output

Sorted numbers: [1, 2, 3, 5, 8]
Sorted fruits: [apple, banana, orange]

Common Pitfalls

Common mistakes when using Arrays.sort include:

• Trying to sort arrays of objects that do not implement Comparable without providing a Comparator.
• Assuming Arrays.sort sorts in descending order by default (it sorts ascending).
• Modifying the array while sorting, which can cause unexpected results.

java

import java.util.Arrays;
import java.util.Comparator;

public class SortPitfalls {
    public static void main(String[] args) {
        // Wrong: sorting objects without Comparable or Comparator
        // class Person {} // no Comparable
        // Person[] people = {new Person(), new Person()};
        // Arrays.sort(people); // This causes compile error

        // Right: use Comparator for custom sorting
        String[] words = {"pear", "apple", "orange"};
        Arrays.sort(words, Comparator.reverseOrder());
        System.out.println("Descending order: " + Arrays.toString(words));
    }
}

Output

Descending order: [pear, orange, apple]

Quick Reference

Method	Description
Arrays.sort(array)	Sorts entire array in ascending order
Arrays.sort(array, fromIndex, toIndex)	Sorts part of array from fromIndex (inclusive) to toIndex (exclusive)
Arrays.sort(array, Comparator)	Sorts array using custom Comparator
Arrays.toString(array)	Converts array to readable string for printing

Key Takeaways

Use Arrays.sort(array) to sort arrays in ascending order easily.

For objects, ensure they implement Comparable or provide a Comparator.

Arrays.sort modifies the original array in place.

Use Arrays.sort(array, Comparator) for custom sorting rules.

Remember to import java.util.Arrays before using Arrays.sort.